ES2575209T3 - Corneal tissue detection and monitoring device - Google Patents

Abstract

Eye surgery laser apparatus, comprising - a laser source (12) for creating a laser beam (14) with a variable wavelength, - optical elements (26) that are adapted to focus a laser beam having a length wavelength and a pulse duration in a focus (80) within a corneal tissue (60-68) of an eye (16), and - a detection element (50) adapted to detect, as an image production signal , a light that is formed as a frequency multiple in the focus (80) and backscattered or emitted forward, in which the light is detected to produce image information on the inner corneal tissue (60-68), in which - the pulse energy of the laser beam (14) or is adjustable so that the beam energy in the focus (80) of the laser beam (14) is at an energy level equal to or greater than the threshold for photodisruption of corneal tissue (60 -68), so that the laser apparatus is usable for therapeutic purposes, or - Pulse energy of the laser beam is adjustable so that the beam energy in the focus (80) of the laser beam (14) is at a lower energy level than the threshold for photodisruption of the corneal tissue (60-68), so that The laser apparatus can be used for preoperative or interoperative diagnostic purposes, in which the variable wavelength is varied depending on the depth of focus (80) within the corneal tissue (60-68) of the eye (16).

Description

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DESCRIPTION

Corneal tissue detection and monitoring device.

In eye surgery, such as in LASIK surgery, information can be collected for use in surgery. For example, the shape or thickness of the corneal tissue can be measured before surgery or the depth of the cuts made during surgery. As another example, images of any scar within the corneal tissue can be taken due to previous surgeries.

As shown in Figure 3, the human cornea has five layers. The outer layer is epithelium 64, a thin layer of rapidly growing and easily regenerating cell tissue, usually composed of approximately six layers of cells. Next is Bowman's layer 62, which is a condensed collagen layer with a thickness of 8-14 mm that protects the stroma. Stroma 60 is a thick, transparent middle layer, which includes regularly arranged collagen fibers (also called "fibrils") and sparsely interconnected keratocytes, which are cells responsible for general maintenance and repair. Descemet membrane 66 is an acellular layer with a thickness of approximately 5-20 mm. Finally, endothelium 68 is an approximately 5 mm thick layer of cells rich in mitochondria.

Stroma 60 is the thickest layer of the cornea, representing up to 90% of the corneal thickness. The stroma is composed of approximately 200 plates of collagen fibrils called "lamellae", superimposed between each other. Each foil has a thickness of approximately 1.5-2.5 mm. The fibers of each lamella are parallel to each other, but generally at right angles to the adjacent lamella fibers. Frequently, the fibers are intertwined between adjacent layers. A remodeling, or reconstruction, of the stroma during surgery alters the ability to focus the light of the cornea, which can correct a patient's vision.

A predominant type of surgery for the reconstruction of the cornea is LASIK (laser-assisted keratomileusis in situ) surgery, which is performed using a laser. LASIK surgery is usually performed in three stages. A first stage creates a flap of corneal tissue. A second stage remodels the cornea under the flap with a laser. In a third stage, the flap is replaced.

Before having LASIK surgery, corneal thickness is usually measured using at least one corneal pachymetry technique. During surgery, the corneal tissue cut can be monitored as well as the reconstruction of the stroma layer. Normally it is desirable that the Descemet membrane and endothelium remain unharmed while the flap is cut and the cornea is reconstructed. However, the known diagnostic systems have limited precision and image resolution and are difficult to integrate with the therapeutic systems used in LASIK surgery.

Known diagnostic devices for preoperative and intraoperative diagnosis of corneal tissue include Scheimpflug cameras and optical coherence tomography (OCT) scanning devices. Scheimpflug cameras used in corneal pachymetry have an image resolution limited to approximately 10 mm. Scheimpflug cameras can be used to detect the position of the external surfaces of the cornea, but do not provide information on the interior structure of the cornea.

Optical coherence tomography is an interferometric technique that is used to capture three-dimensional images from within optical dispersion media, such as biological tissue. For applications in corneal pachymetry, OCT scanning devices have a resolution of approximately 5-10 mm, which can be increased to approximately 1-2 mm with known technologies. The wavelengths used for detection are normally in the 800-1300 nm range.

OCT scanning devices generate signals by detecting significant differences in refractive indices of adjacent tissues. The different refractive indices of adjacent tissues cause phase shifts of the reflected, or backscattered light. However, tissue structures at a sub-micrometric scale and tissue boundaries that are not distinguished by a large difference in their refractive index cannot be detected. For example, using an OCT scanning device, the position and structure of the stromal collagen fibrils and the layered structure of the human cornea cannot be detected.

Scheimpflug cameras and OCT scanning devices use wavelengths that overlap with the wavelength range used by surgical microscopes, for example, in the visual range of 420 nm to 700 nm. Therefore, the use of these detection devices intraoperatively can cause interference between the systems, which leads to a reduction in accuracy in measurement and / or compromised image quality.

The document by Han et al., Second-harmonic Imaging of Cornea Intra-stromal Femtosecond Laser Ablation, Journal of Biomedical optics Vol. 9, No. 4, 760-766, refers to obtaining images of the second harmonic of the cornea after laser ablation of intrastromal femtoseconds. To surgically treat a sample

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corneal, in particular, for an intrastromal ablation and flap cutting, a neodymium-crystal laser (Nd: crystal) is used that provides light with a wavelength of 1060 nm and an impulse duration of 700 fs; The laser beam is guided to the eye through a pair of lenses with a variable focal length (Z scan) and two galvanometric mirrors that allow a quick XY scan. The diameter of the laser point in the focal plane is 5 mm. For the generation of images by generation of the second harmonic (SHG), a multifontic laser scanning microscope is used that has a titanium-sapphire laser (Ti: Sa), which can be configured from 700 to 1000 nm, as a source of excitation laser with a laser emission wavelength set at 880 nm.

WO 2008/002278 A1 refers to optical imaging systems for the analysis of biological tissue with a high coefficient of optical dispersion such as liver tissue. A nonlinear optical microscopic apparatus obtains images of a sample by exciting sHg light in the sample in response to the excitation light of an excitation source, which is a pulsed laser excitation source, in which the power of the Excitation light that affects the sample is such that it does not cause optical damage to the sample such as, for example, thermal denaturation. Then the SHG light that is emitted from the sample is collected by a first optical condensing element and detected by a sensitive optical detector.

The document by Aptel et al., Multimodal Nonlinear Imaging of the Human Cornea, Investigative Ophthalmology and Visual Science, Vol. 51, No. 5, 2459-2465, refers to obtaining nonlinear and multimodal images of the human cornea . The imaging is done in a SHG microscope and by generation of the third harmonic (THG) laser scan equipped with detection channels in the direction back and forth. The excitation is performed using a Ti: Sa oscillator and an optically parametric oscillator that is pumped synchronously that supplies pulses of 100 to 150 fs in the focus of a target. The microscope incorporates galvanometric mirrors, motorized water immersion objectives and photomultiplier modules photon counters. For obtaining THG images, excitation wavelengths of redshift of normally 1200 nm are used so that higher impulse energies can be used while maintaining cell viability, in which obtaining images of SHG is performed with 860 nm excitation light.

US 2005/0063041 A1 refers to a technique of obtaining images by microscope using both second and third harmonic waves of a laser beam excitation spectrum by means of a sample to form an image of the sample. A microscope imaging system comprises an scanning device that receives the laser beam from a short pulse laser device. The laser beam, which is directed to the microscope by the scanning device, is focused by a microscope objective lens on a biological sample. The laser beam has a predetermined wavelength, preferably 1230 nm. The second and third harmonic wave components are directed to photodetectors and become corresponding electrical signals, which are then processed to generate an image of the sample.

The document by Han et al., Second Harmonic Generation Imaging of Collagen Fibrils in Cornea and Sclera, Optics Express, Vol. 13, No. 15, pages 5791-5797, refers to the obtaining of images by second harmonic generation of Collagen and sclerotic collagen fibrils. The imaging of SHG is performed with a multifontic laser scanning microscope equipped with a Ti: Sa laser of femtoseconds in a locked way with a laser emission wavelength set at 800 nm. A water immersion lens is used to focus the excitation beam and to collect the return SHG signals, which are directed to a photomultiplier tube detector.

The document of Tan et al., Characterizing the Thermally Induced Structural Changes to Intact Porcine Eye, Part 1: Second Harmonic Generation Imaging of Cornea Stroma, Journal of Biomechanical Optics, Vol. 10, No. 5, pages 054019-1 to 054019 -5, refers to obtaining images by generating a second harmonic stroma of the cornea. The SHG microscope is a multifotonic microscope, in which an output at 880 nm of a solid state laser pumped by diode pumps a Ti: Sa laser, which is used as a source of SHG. An average power of approximately 24 mW is used in the sample for the generation of a second harmonic signal and the SHG signal generated from the cornea collagen fibers is collected with backscatter geometry and detected by a multiplier tube of collecting individual photons.

Providing a separate diagnostic device, in addition to the therapeutic device, such as a femtosecond pulse laser, increases the total cost of the equipment required to perform the surgery.

WO 2011/103357 discloses an optical coherence tomography system for ophthalmic surgery. It shows, among other things, a system guided by imaging, which uses a single pulsed laser to produce light or surgical or imaging.

Therefore, an object of examples of the invention is to provide a laser eye surgery apparatus that improves existing devices by enhancing precision in measurement and / or use during surgery.

This object is achieved by means of a laser eye surgery apparatus according to claim 1.

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According to a first aspect of the invention, an eye surgery laser apparatus according to claim 1 is provided. The apparatus comprises optical elements that are adapted to focus a laser beam having a wavelength and a pulse duration at a focus within a corneal tissue of one eye. In addition, the apparatus comprises a detection element adapted to detect, as an image production signal, light that is formed, in the focus, as a frequency multiplex and backscattered to produce image information on the inner corneal tissue.

The detection of backscattered light at a multiple frequency allows the capture of images with high resolution, since the light at a multiple frequency has a shorter wavelength, and therefore provides an improved image resolution.

In an embodiment of the first aspect, the optical elements can be adapted to focus the laser beam successively on an additional focus, which can be located at a depth different from the depth of the previous focus. The detection element is adapted to detect, as an additional signal that produces images, light that is formed in said additional focus, such as a frequency multiple and backscattered or emitted forward, to produce said image information on the inner corneal tissue. The collection of backscattered light from two different depths of focus allows the formation of a three-dimensional image by, for example, the computational combination of the image signals of both depths.

In a further embodiment of the first aspect, the optical elements can be adapted to focus the laser beam successively towards a plurality of foci at varying depths within the corneal tissue of the eye. The detection element can be adapted to detect, as image production signals, light that is formed, in each of said foci, as a frequency multiplex and backscattered or emitted forward, to gather three-dimensional image information on the corneal tissue inside. The collection of backscattered light from a plurality of depths of focus allows the formation of three-dimensional images by, for example, the computational combination of the image signals of the plurality of depths.

The use of the laser eye surgery apparatus described above for the exploration of the inner corneal tissue of an eye allows the detection of backscattered light at a multiple of frequency, which can be used to produce high resolution images of corneal tissue while minimizing interference with the microscope of the operation.

The laser eye surgery apparatus described above can be used for pre or intraoperative diagnostic purposes. The wavelength of the laser beam is selected so that the beam energy at the focus of the laser beam is lower than an energy required for photodisruption of the corneal tissue.

The method of scanning a corneal tissue of an eye is not part of this invention. A laser beam that has a wavelength and a pulse duration focuses on a focus within a corneal tissue of an eye. A light that is formed, in the spotlight, as a multiple frequency and backscattered is detected as an image production signal, to produce image information about the inner corneal tissue.

The detection of backscattered light at a multiple frequency allows the capture of images with high resolution, since the light at a multiple frequency has a shorter wavelength, which normally provides an improved image resolution.

In this method, the laser beam can focus successively on an additional focus, which is located at a depth different from the depth of the previous focus. A light is then detected that is formed, in the additional focus, as a frequency multiplex and backscattered, as an additional signal that produces images and can be used to produce image information about the inner corneal tissue. The collection of backscattered light from two different depths of focus allows the formation of a three-dimensional image by, for example, the computational combination of the image signals of both depths.

More generally, the laser beam can focus successively towards a plurality of foci located at different depths within the corneal tissue of the eye, and the light that forms, in each of the foci, can be detected as a frequency multiple and backscattered as a image production signal, and is collected to produce three-dimensional image information on the inner corneal tissue. The collection of backscattered light from a plurality of depths of focus allows the formation of three-dimensional images by, for example, the computational combination of the image signals of the plurality of depths.

In any of the above aspects and embodiments, the plurality of foci may be in the stroma of the eye, thus allowing a high resolution detection and a monitoring of layers and / or structures within the stroma.

In any of the above aspects and embodiments, the laser source is adapted to create a laser beam with variable wavelengths. In other words, the laser source is adapted to create a laser beam with

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a variable impulse energy. Since the pulse energy of the laser beam depends on its wavelength, in the context of this application, the terms "variable wavelength" and "variable pulse energy" can be used interchangeably. Providing a variable wavelength / variable pulse energy allows the use of the laser source both for diagnostic and therapeutic purposes.

As for diagnostic purposes, the laser source can be set to a wavelength and / or a pulse duration corresponding to a low energy, for example, the energy threshold is I <1012 W / cm2, which will not cause photodisruption to the cornea, and image information of backscattered light is collected at a frequency multiple. For example, in terms of diagnostic purposes, a wavelength of approximately 920 nm and an impulse duration of between 150-180 fs can be set; more generally, any wavelength and / or pulse duration is conceived which results in an energy that is lower than the energy threshold at which stromal photodisruption occurs, for example the energy threshold may be I <1012 W / cm2

As for therapeutic purposes, the laser source can be set to a wavelength and / or pulse duration corresponding to an energy high enough to cause corneal photodisruption, for example, the energy threshold is I> 1012 W / cm2. For example, as for therapeutic purposes, a wavelength of approximately 1030 nm and an impulse duration of approximately 300 or 350 fs can be set; more generally, any wavelength and / or pulse duration that results in an energy that is equal to or greater than the energy threshold at which stromal photodisruption occurs, for example, the energy threshold may be I <1012 W / cm2

In any of the above aspects and embodiments, the variable pulse wavelength / energy is varied depending on the depth of focus within the corneal tissue of the eye. The wavelength can be variable between 700 and 1050 nm, or it can remain at a particular wavelength such as 710 nm, 820 nm, 920 nm or 1030 nm. Shorter wavelengths such as 700 nm produce higher resolution image signals, while longer wavelengths such as 1050 nm can penetrate deeper into the corneal tissue. The succession of wavelengths of 710 nm, 820 nm, 920 nm and 1030 nm allows a complete scan of the cornea to be carried out, while maintaining a high image resolution.

In any of the above aspects and embodiments, the pulse duration of the laser beam can be a pulse duration of femtoseconds between 10 and 400 fs, for example, 100 fs, 350 fs. This pulse duration provides enough energy to produce multiples of frequency of the initial wavelength and backscatter to the detection unit, but ensures that the total energy of a laser pulse remains below the threshold of corneal tissue photodisruption Of the eye.

In any of the above aspects and embodiments, the pulse energy of the laser beam can be set so that the beam energy in the focus of the laser beam is at a lower energy level than the threshold for photodisruption of the corneal tissue, so that the device can be used for preoperative or interoperative diagnostic purposes. Alternatively or additionally, when the apparatus is not being used for diagnostic purposes during surgery, the pulse energy of the laser beam can be set so that the beam energy at the focus of the laser beam is at an energy level that is equal to or greater to the threshold for photodisruption of the corneal tissue, so that the apparatus can be used for therapeutic purposes.

In any of the above aspects and embodiments, the frequency multiple may be one signal per second harmonic generation (SHG) or by third harmonic generation (THG).

The invention is defined in the claims and will be further explained based on the attached figures, which are schematic in their entirety.

Figure 1a shows a schematic block representation of elements of a laser system for eye surgical treatments.

Figure 1b shows a schematic block representation of elements of a laser system according to a variant of the laser system shown in Figure 1a.

Figure 2 shows a schematic diagram of the cornea of a human eye.

Figure 3 shows the corneal tissue layers along the cross-section A-A 'of the eye shown in the figure

2.

Figure 4 shows a block diagram illustrating the components of the laser apparatus shown in Figure 1a.

Figures 1a and 1b show a laser system 10 comprising a laser apparatus for focusing a laser beam 14

at a point of focus within an eye 16.

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The laser system comprises a laser source 12. The laser source 12 may include, for example, a laser oscillator (eg, solid state laser oscillator); a preamplifier, which increases the pulse power of the laser pulses emitted from the oscillator and simultaneously stretches them temporarily; a rear pulse selector, which selects laser pulses from the preamplified laser pulses of the oscillator to reduce the repetition rate to a desired degree; a power amplifier, which amplifies the selected pulses, still temporarily stretched, up to the pulse energy needed for the application; and a pulse compressor, which temporarily compresses the pulse emission from the power amplifier to the desired pulse duration for the application.

The laser source 12 generates a pulsed laser beam 14. The pulse duration of the radiation pulses is chosen either to generate signals of reflected or backscattered light for diagnostic purposes or to create incisions in the corneal tissue of an eye 16 of a patient for treatment purposes. The radiation pulses of the laser beam 14 have a pulse duration in the range of nanoseconds, picoseconds, femtoseconds or attoseconds.

In addition, the laser beam 14 generated by the laser source 12 has a pulse repetition rate suitable for the particular application. The repetition rate of the radiation pulses emitted from the laser device 10 and directed over the eye 16 may correspond to the repetition rate of the radiation pulses that are generated in the emission of the laser source 12. Alternatively, a part of the radiation pulses that are emitted from the laser source 12 can be blocked by means of an optical switch 18 arranged in the radiation path of the laser beam 14 so that they do not reach the eye 16. This may be necessary. , for example, for a predetermined machining profile of eye 16.

The optical switch 18, also called the pulse modulator, can be, for example, an acoustic-optical modulator or an electro-optical modulator. Generally, optical switch 18 may include arbitrarily optically active elements that allow rapid blocking of individual laser pulses. The optical switch 18 may include, for example, a beam trap, indicated schematically at 20, which serves to absorb the radiation pulses to be blocked. The optical switch 18 may deflect such radiation pulses from the normal beam path of the radiation pulses of the laser beam 14 and direct them to the beam trap 20.

Additional optical components that are arranged in the beam path of the laser beam 14 include a z 22 controller and an x-y 24 controller. The z 22 controller, on the one hand, controls the longitudinal location of the focal point of the laser beam 14; The x-y 24 controller, on the other hand, controls the transverse location of the focal point.

In Figures 1a and 1b a coordinate frame has been drawn that represents the directions of x-y-z in the region of the eye 16 for purposes of illustration. In this context, the term "longitudinal" refers to the direction of beam propagation, which is conventionally designated as the direction of z. Similarly, "transverse" refers to a direction transverse to the direction of propagation of the laser beam 14, which is conventionally designated as the x-y plane.

To achieve a transverse deviation of the laser beam 14, the x-y controller 24 may include, for example, a pair of galvanometric actuation scanning mirrors that can be tilted around mutually perpendicular axes. The z controller 22 may include, for example, a longitudinally adjustable lens or a lens of variable refractive power or a deformable mirror with which the divergence of the laser beam 14 can be controlled, and therefore the position of z of the beam focus. Such a lens or mirror may be included in a beam expander that expands the laser beam 14 emitted from the laser source 12. The beam expander can be configured, for example, as a Galileo telescope.

The laser apparatus of the embodiments shown in Figures 1a and 1b comprises a focusing lens 26 arranged in the beam path of the laser beam 14. The focusing lens 26 serves to focus the laser beam 14 on a desired location on or inside eye 16, as well as inside the cornea. The focus objective 26 may be an f-theta focus objective.

The optical switch 18, the z controller 22, the x-y controller 24 and the focus lens 26 need not be arranged in the order shown in Figures 1a and 1b. For example, the optical switch 18 can be arranged, without losing the generality, in the beam path downstream of the controller of z 22. If desired, the controller of xy 24 and the controller of z 22 can be combined to form a unit unique structural. The order and grouping of the components shown in Figures 1a and 1b should not be understood at all as restrictive.

On the beam exit side of the focusing lens 26, a flattening element 30a constitutes a stop contact surface with the cornea of the eye 16. The flattening element 30a is transparent or translucent to laser radiation. On the lower side, facing the eye, the flattening element 30a includes a stop face 32a with the cornea of the eye 16. In the exemplary case shown, the stop face 32a is realized as a flat surface. In certain embodiments, the stop face 32a is concave or convex. The stop face 32a levels the cornea when the flattening element 30a is pressed against the eye 16 with an appropriate pressure or

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when the cornea is aspirated on the abutment face 32a by vacuum. As shown in Figures 1a and 1b, the eye 16 rests against the flat stop face 32a of the flattening element 30a.

The flattening element 30a, which in the case of design parallel to the plane is usually referred to as a flattening plate, conforms to the narrower end of a carrier sleeve 34a that conically widens. The connection between the flattening element 30a and the carrier sleeve 34a can be permanent, for example by means of adhesion fixation, or it can be detachable, for example, by means of a screw coupling. It is also conceivable to use a single injection molded optical part that functions as a carrier sleeve 34a and as a flattening element 30a. In a manner not shown in detail, the carrier sleeve 34a has coupling structures at its wider sleeve end, which in the drawings is the upper end. The coupling structures are suitable for coupling the carrier sleeve 34a on the focus lens 26.

The laser system 10 also comprises at least one detection element 50 that is adapted to detect light, which is formed as a frequency multiple in the focus and backscattered to the detection element 50, so as to produce image information about the inner corneal tissue. The detection element 50 may be located either inside or outside the carrier sleeve 34a.

In the embodiment shown in Figure 1 b, a beam splitter 51, which may be a dichroic splitter, is provided in the beam path, and the detection element 50 is located in a position such that a portion of light deflected by the beam splitter 51 deflects on the detection element 50. In other words, the detection element 50 can be arranged so that the backscattered light, which is formed as a frequency multiple, is directly backscattered to the detection element 50 ( figure 1a). Alternatively, the detection element 50 may be arranged so that the backscattered light is backscattered to the beam splitter 51 arranged in the beam path and then deflected to the detection element 50 (Figure 1b). The detection element 50 is a photodetector, for example, a photomultiplier tube (PMT), an avalanche photodiode (APD), a high gain silicon photomultiplier (SPM), or any other light amplifying sensor.

The laser source 12, the optical switch 18, the detection element 50 and the two scanning devices 22, 24, are controlled by a control computer 36, which operates according to a control program 40 stored in a memory 38. The control program 40 contains instructions (for example, program code) that are executed by the control computer 36 to control the location of the beam beam of the laser beam 14 in the cornea, in the lens or in any other location of the eye 16 which rests against the contact element 30a.

The laser system 10 may also comprise an interface module (not shown) connected to the control computer 36 to allow a user to enter orders into the control computer 36. The interface module may comprise a screen or monitor to allow the user to view the status information of the components of the laser system and / or the data collected by at least one of the detection elements 50.

Figures 2 and 3 schematically illustrate the cornea of a human eye. To illustrate the layers of the cornea, in Figure 3 the layers of the cornea of the eye 16 are shown enlarged, as explained in the introduction.

Figure 4 schematically illustrates the components of the laser apparatus. As shown in FIG. 4, the laser apparatus comprises optical elements 42 that are adapted to focus a laser beam 14 within a corneal tissue of an eye 16. The optical elements 42 comprise at least the z controller 22 and the objective. 26 of focus of the laser system 10 of figures 1a and 1b, but can also comprise the laser source 12, the pulse width modulator 18 and / or the xy controller 24 shown in figures 1a and 1b.

The laser apparatus also comprises at least one detection element 50, which is adapted to detect the light that is formed as a frequency multiple in the focus and is backscattered or emitted forward towards the detection element, to produce image information on the inner corneal tissue.

When the laser apparatus is used for therapeutic purposes, a beam 14 is generated with sufficient beam energy at the focus 80, which is located at a depth 82, to cut an incision pattern. During machining of the cornea, such an incision pattern completely cuts a volume of corneal tissue from the underlying corneal tissue, as part of a corneal lenticular extraction or a corneal keratoplasty. If desired, this incision pattern can further subdivide the volume of tissue cut into a plurality of volume segments individually separated from each other.

When the laser apparatus is used for diagnostic or scanning purposes, an intense light in the focus 80 of the laser beam 14 causes highly polarized and non-centrometric fabrics, such as collagen, to produce light at a multiple frequency of the input frequency .

Higher frequency light is partially produced in the form of signals by second harmonic generation (SHG), which are created when two near-infrared photons interact with highly polarized, non-centimeter materials, to generate a single visible photon with twice as much energy and half wavelength.

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Higher frequency light can also be produced in the form of signals by generation of third harmonic (THG), which are created when three near-infrared photons interact with highly polarized non-centered materials to generate a single visible photon with triple energy and a third Part of the wavelength. Although only SHG and THG signals are described in detail herein, it is indicated that other higher order harmonic signals are also possible.

The light inside the laser beam 14 causes collagen structures of the cornea that are located within the focus 80 to emit photons at multiples of the frequency of the light that forms the laser beam 14. In one example, if the light within the laser beam 14 has a wavelength of 1 = 1030 nm, then a SHG signal is produced at the frequency 1shg = 515 nm, and a THG signal is produced at 1thg = 343 nm.

When excited by laser beam 14, higher frequency light is emitted in the form of SHG and THG signals from the collagen structures of the cornea. The higher frequency light disperses in all directions producing signals in the form of backscattered beams 86. The detection element 50 detects these signals and uses them to produce image information on the inner corneal tissue.

The focus diameter 80 of the laser beam 14 can be between about 1 mm and 10 mm. The diameter of the focus 80 of the laser beam 14 is selected to exceed the size of the structures or cells to be examined, for example, the diameter of the focus 80 can be set to 1.5 mm.

The z 22 controller of the laser system 10 is adapted to vary the depth 82 of the focus 80 within the eye 16. In addition, the laser source 12 of the laser system 10 is adapted to vary the wavelength of the light in the laser beam 14.

During diagnostic use, the wavelength of the light in the laser beam 14 can be varied between 700 and 1050 nm according to the depth of focus 80 within the eye 16. Light with longer wavelengths travels more easily through of the material of the eye 16, and therefore longer wavelengths can be used to examine the material that is further removed from the outer surface of the eye 16.

In addition, the pulse modulator 18 of the laser system 10 is adapted to vary the pulse energy of the laser beam 14. For example, the pulse energy of the laser beam 14 may range between 0.5 | mJ and 0.05 mJ.

In the operation, a diagnostic scan can be performed by varying the pulse energy of the laser beam 14, so that the beam energy at the focus 80 of the laser beam 14 is lower than an energy required for photodisruption of the corneal tissue. The laser beam 14 is then focused on a focus 80 within the cornea of the eye 16, and the backscattered light 86 that is formed as a frequency multiple in the focus 80 is detected by the detection element 50 as a signal producing images, to produce image information about the inner corneal tissue.

To collect three-dimensional image information, the laser beam 14 focuses successively on foci 80 of varying depth 82 within the cornea. When diagnostic scans are performed, the laser beam operates in a wavelength range between 700 and 1050 nm. At successive depths 82, the wavelength of the light forming the laser beam 14 is increased as the distance of the focus 80 from the outer surface of the eye 16 increases. Alternatively, a single wavelength can be used in the range of 7001050 nm for multiple depths 82 or for all depths 82 within the eye 16.

After completing the diagnostic scan of the corneal tissue, the pulse energy of the laser beam 14 is increased, so that the beam energy at the focus 80 of the laser beam 14 exceeds the energy required for photodisruption of the corneal tissue. At this point, surgery can be started or resumed, and the laser system 10 is used to cut and / or reconstruct the corneal tissue.

In summary, the pulse energy of the laser beam 14 can be chosen so that the beam energy at the focus 80 of the laser beam 14 is above or below the collagen photodisruption energy. As such, the laser apparatus can alternatively be used to either cut / rebuild corneal tissue during surgery or to generate SHG / THG signals that are collected by the detection element 50 to produce diagnostic information about the cornea. In this way, a single laser system 10 can be used alternately to provide either diagnostic or therapeutic functionality.

Claims (6)

5 10 fifteen twenty 25 30 35 40 1. Laser eye surgery device, comprising - a laser source (12) to create a laser beam (14) with a variable wavelength, - optical elements (26) that are adapted to focus a laser beam having a wavelength and a pulse duration in a focus (80) within a corneal tissue (60-68) of an eye (16), and - a detection element (50) adapted to detect, as an image production signal, a light that is formed as a frequency multiple in the focus (80) and backscattered or emitted forward, in which the light is detected for produce image information about the inner corneal tissue (60-68), in which - the pulse energy of the laser beam (14) or is adjustable so that the beam energy in the focus (80) of the laser beam (14) is at an energy level equal to or greater than the threshold for photodisruption of corneal tissue ( 60-68), so that the laser apparatus is usable for therapeutic purposes, or - the pulse energy of the laser beam is adjustable so that the beam energy at the focus (80) of the laser beam (14) is at an energy level below the threshold for photodisruption of corneal tissue (60-68), of so that the laser apparatus is usable for preoperative or interoperative diagnostic purposes, in which the variable wavelength is varied depending on the depth of focus (80) within the corneal tissue (6068) of the eye (16). 2. Laser apparatus according to claim 1, wherein the optical elements (26) are adapted to focus the laser beam (14) successively on a plurality of foci at varying depths within the corneal tissue (60-68) of the eye (16 ), in which the detection element (50) is adapted to detect, as image production signals, a light that is formed as a frequency multiple in each of said foci (80) and backscattered or emitted forward, in which the light is detected to collect three-dimensional image information on the inner corneal tissue (60, 62, 66). 3. Laser apparatus according to claim 2, wherein the plurality of foci (80) are in the stroma (60) of the eye (16). 4. Laser apparatus according to one of the preceding claims, wherein the wavelength is variable between 700 and 1050 nm. 5. Laser apparatus according to one of the preceding claims, wherein a pulse duration of femtoseconds is between 10 and 400 fs. 6. Laser apparatus according to one of the preceding claims, wherein the frequency multiple is a signal by generation of the second harmonic (SHG) or by generation of the third harmonic (THG).